Pixel structure

ABSTRACT

A pixel structure includes a scan line, a data line, a gate electrode electrically connected to the scan line, a semiconductor layer disposed on the gate electrode, a drain electrode, an extending electrode, and a pixel electrode. The scan line and the data line cross each other, and are insulated. The drain electrode includes a contact part disposed outside the gate electrode, an electrode part disposed on the semiconductor pattern and a connecting part extending from the contact part along a direction to connect the electrode part, and partially overlapping the gate electrode. The pixel electrode is connected to the contact part. The extending electrode is connected to the scan line. A first end of the extending electrode points to the semiconductor layer along the direction, and overlaps the drain electrode. A first width of the connecting part is equal to the second width of the extending electrode.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/CN2009/076055 filed Dec. 25, 2009.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a pixel structure, and moreparticularly, to a pixel structure having a constant gate-drainparasitic capacitance.

2. Description of the Prior Art

Conventional TFT-LCD (thin film transistor liquid crystal display)includes a TFT array substrate, a counter substrate and a liquid crystallayer sandwiched in-between. The TFT array substrate includes aplurality of scan lines, a plurality of data lines, a plurality of TFTsdisposed between the scan lines and the data lines and a pixel electrodedisposed corresponding to each TFT. The counter substrate includes acommon electrode. Each aforementioned TFT includes a gate electrode, asemiconductor layer, a source electrode and a drain electrode, andfunctions as a switching element of a liquid crystal unit.

The manufacturing process of the TFT array substrate usually includes aplurality of exposure, photolithography and etching processes. Ingeneral manufacturing technology, the gate electrode and the scan lineare formed by a first metal layer, and the source electrode, the drainelectrode and the data line are formed by a second metal layer. At leastan inter-layer dielectric (ILD) layer is disposed between the firstmetal layer and the second metal layer. In the TFT structure, the gateelectrode at least partially overlaps the drain electrode; therefore,the so-called gate-drain parasitic capacitance (Cgd) exists due to theoverlapping of the gate electrode and the drain electrode.

With regard to the LCD, a voltage transferred from the data line isapplied to a liquid crystal capacitor Clc formed by the pixel electrode,the common electrode and the liquid crystal layer; and the voltage has aspecific relation to a transmittance of liquid crystal molecules in theliquid crystal layer. The voltage applied to the liquid crystalcapacitor Clc depends on grayscale values of an image displayed.However, due to the existence of the gate-drain parasitic capacitance,the voltage difference on the liquid crystal capacitor Clc will varywhen the signal on the gate line varies. The voltage change is known asthe feed-through voltage ΔVp, and can be represented by an equationbelow.ΔVp=[Cgd/(Clc+Cgd+Cst)](Vgon−Vgoff)

Where Vgon−Vgoff represents an amplitude of a voltage pulse applied onthe scan line, and Cst stands for a storage capacitor.

During the TFT manufacturing process, a misalignment by the machinemovement may cause the TFT components to deviate from their designatedpositions. Especially, an overlapping area of the gate electrode and thedrain electrode varies, therefore, the gate-drain parasitic capacitanceCgd varies as well and different pixels have different feed-throughvoltages ΔVp. A problem of display picture quality degradation isgenerated during displaying; therefore, an objective for the TFTs tokeep the gate-drain parasitic capacitances (Cgd) stable is desired.

SUMMARY OF THE INVENTION

The present invention provides a pixel structure capable of ensuringstability of the gate-drain parasitic capacitances when misalignment isgenerated.

According to a preferred embodiment of the present invention, a pixelstructure is provided. The pixel structure includes a scan line, a dataline, a gate electrode, a semiconductor layer, a source electrode, adrain electrode, an extending electrode and a pixel electrode. The scanline and the data line cross each other, and are electrically insulatedfrom each other. The gate electrode is electrically connected to thescan line. The semiconductor layer is disposed on the gate electrode.The source electrode has at least a portion disposed on thesemiconductor layer, and the drain electrode has at least a portiondisposed on the semiconductor layer. The source electrode is connectedto the data line. The drain electrode includes a contact part, anelectrode part and a connecting part. The contact part is disposedoutside the gate electrode. The electrode part is disposed on thesemiconductor layer. The connecting part extends from the contact partalong a direction to connect the electrode part, and overlaps a portionof the gate electrode. The connecting part has a first width. Theextending electrode is connected to the scan line. The extendingelectrode has a first end, and the first end points to the semiconductorlayer along the direction and overlaps the drain electrode. Theextending electrode has a second width, and the first width of theconnecting part is substantially equal to the second width. The pixelelectrode is connected to the contact part of the drain electrode.

In an embodiment of the present invention, the pixel structure furtherincludes a semiconductor pattern, disposed between the extendingelectrode and the drain electrode, and located at an overlapping area ofthe extending electrode and the drain electrode.

In an embodiment of the present invention, the extending electrode has asecond end away from the first end, and the second end is connected tothe scan line. For example, the extending electrode is L-shaped.Furthermore, the extending electrode is substantially U-shaped.

In another embodiment of the present invention, the electrode part ofthe drain electrode is a U-shaped part surrounding the source electrode,and the U-shaped part has a base and two branches extending from twoends of the base toward the direction. The connecting part of the drainelectrode is connected to the base or one of the branches of theU-shaped part.

In another embodiment of the present invention, the source electrode isU-shaped so that it surrounds the electrode part of the drain electrode.The electrode part of the drain electrode and the connecting part areconnected to each other, and form a strip pattern.

In another embodiment of the present invention, the drain electrodefurther includes a protrusion part, the contact part is disposed betweenthe connecting part and the protrusion part, and the protrusion part isparallel to the direction and overlaps the extending electrode.

In another embodiment of the present invention, the drain electrodefurther includes a protrusion part paralleled to an edge of the gateelectrode and located outside the gate electrode which is not overlappedby the protrusion part, and the protrusion part is connected to thecontact part and overlaps the extending electrode.

In another embodiment of the present invention, the contact part, theelectrode part and the connecting part of the drain electrode are formedintegrally.

In another embodiment of the present invention, the source electrode andthe data line are formed integrally.

In another embodiment of the present invention, the gate electrode is aportion of the scan line, and the extending electrode is connected tothe gate electrode.

In another embodiment of the present invention, the gate electrodeextends from the scan line to form at least a portion of the gateelectrode outside the scan line.

As mentioned above, the present invention disposes an extendingelectrode connected to the scan line or the gate electrode, and an endof the extending electrode overlaps the drain electrode. When therelative position between the gate electrode and the drain electrodevaries due to the misalignment in the manufacturing process, thegate-drain parasitic capacitances still are the same as that of thepredetermined layout. For this reason, the pixel structure has a hightolerance for the misalignment, and keeps a stable display picturequality.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic diagram illustrating a sectional top view of apixel structure according to a first embodiment of the presentinvention.

FIG. 2 is a cross-sectional view of the pixel structure, taken along aline AA′ of FIG. 1.

FIG. 3 is a schematic diagram illustrating a sectional top view of apixel structure according to a second embodiment of the presentinvention.

FIG. 4 is a sectional top view of a pixel structure according to a thirdembodiment of the present invention.

FIG. 5 is a schematic diagram showing a sectional top view of a pixelstructure according to a fourth embodiment of the present invention.

FIG. 6 depicts a sectional top view of a pixel structure according to afifth embodiment of the present invention.

DETAILED DESCRIPTION

FIG. 1 shows a schematic diagram illustrating a sectional top view of apixel structure according to a first embodiment of the presentinvention. FIG. 2 is a cross-sectional view of the pixel structure,taken along a line AA′ of FIG. 1. As shown in FIG. 1 and FIG. 2, a pixelstructure 100 includes a scan line 110, a data line 120, a gateelectrode 130, a semiconductor layer 140, a source electrode 150, adrain electrode 160, an extending electrode 170 and a pixel electrode180. The scan line 110 and the data line 120 cross each other, and areelectrically insulated from each other. The gate electrode 130 iselectrically connected to the scan line 110. The semiconductor layer 140is disposed on the gate electrode 130. The source electrode 150 has atleast a portion disposed on the semiconductor layer 140, and the drainelectrode 160 has at least a portion disposed on the semiconductor layer140. The source electrode 150 is connected to the data line 120. Theextending electrode 170 is connected to the scan line 110, and the pixelelectrode 180 is electrically connected to the drain electrode 160. Inaddition, the pixel structure 100 further includes a semiconductorpattern 190. The semiconductor pattern 190 is disposed between theextending electrode 170 and the drain electrode 160 (FIG. 2), and isdisposed at an overlapping area of extending electrode 170 and the drainelectrode 160 (FIG. 1). The gate electrode 130, the semiconductor layer140, the source electrode 150 and the drain electrode 160 constitute athin-film transistor (TFT). When the pixel structure 100 displays animage, the TFT can be turned on to transfer a signal on the data line120 to the pixel electrode 180.

The drain electrode 160 of this embodiment includes a contact part 162,an electrode part 164 and a connecting part 166. The contact part 162 isdisposed outside the gate electrode 130, and the electrode part 164 isdisposed on the semiconductor layer 140. The connecting part 166 extendsalong a direction D from the contact part 162 to connect the electrodepart 164, and partially overlaps the gate electrode 130. In thisembodiment, the contact part 162 is a part of the drain electrode 160being in contact with the pixel electrode 180, and the electrode part164 is apart disposed on the gate electrode 130 and being in contactwith the semiconductor layer 140. Furthermore, a distance between theelectrode part 164 and the source electrode 150 is fixed, and the TFThas a good operating efficiency.

In this embodiment, the gate electrode 130 and the extending electrode170 directly extend from the scan line 110, so that a portion of thegate electrode 130 and a portion of the extending electrode 170 areformed outside the scan line, and the scan line 110 is electricallyconnected to the gate electrode 130 and the extending electrode 170respectively. Generally, in a manufacturing process of the pixelstructure 100, the scan line 110, the gate electrode 130 and theextending electrode 170 are formed by patterning a first metal layer,and the data line 120, the source electrode 150 and the drain electrode160 are formed by patterning a second metal layer. In addition, a personskilled in the art should know that at least one dielectric layer isfurther disposed between the first metal layer and the second metallayer, and at least one dielectric layer is further disposed between thesecond metal layer and the pixel electrode 180 in order to maintainelectrical characteristics of each component in the pixel structure 100.

Especially, since the scan line 110, the gate electrode 130, and theextending electrode 170 are formed by using of a photolithographic andetching process through a mask on the first metal layer, a relativestable position among the scan line 110, the gate electrode 130 and theextending electrode 170 will be obtained. Subsequent the foregoingmentioned mask process, a photolithographic and etching process througha different mask on the second metal layer is performed to form the dataline 120, the source electrode 150, and the drain electrode 160, thus, arelative stable position among the data line 120, the source electrode150, and the drain electrode 160 will be obtained as a result ofapplying the same mask. As we can see from the above, when the gateelectrode 130 and the drain electrode 160 are formed by two differentphotolithographic and etching processes with two different masks, amisalignment of the two masks occurs in the alignment step causing theposition between the gate electrode 130 and the drain electrode 160 toskew from its predetermined layout. For this reason, the overlappingarea of the gate electrode 130 and the drain electrode 160 is differentfrom the predetermined design area, and each different pixel may have adifferent overlapping area of the gate electrode 130 and the drainelectrode 160, i.e. a different pixel may have a different gate-drainparasitic capacitance. In the prior art, different gate-drain parasiticcapacitances in different pixels have a negative impact on the displaypicture quality of the pixel structure 100. Therefore, the pixelstructure 100 of this embodiment has the extending electrode 170 to helpkeep the gate-drain parasitic capacitance stable.

Specifically, a relation between the extending electrode 170 and thedrain electrode 160 of this embodiment will be described as follows. Theextending electrode 170 has a first end 172, and the first end 172points to the semiconductor layer 140 along the direction D and overlapsthe contact part 162 of the drain electrode 160. The extending electrode170 substantially has an L-shaped pattern. The extending electrode 170has a second end 174, and the second end 174 away from the first end 172is directly connected to the scan line 110. Accordingly, the extendingelectrode 170 has an identical electric potential with the scan line 110or the gate electrode 130. Because the extending electrode 170 isconnected to the scan line 110 to electrically connect the gateelectrode 130, and a semiconductor pattern 190 is disposed between theextending electrode 170 and the contact part 162, an effect of acapacitor due to the overlapping of the extending electrode 170 and thedrain electrode 160 is substantially equivalent to an effect of thecapacitor due to the overlapping of the gate electrode 130 and the drainelectrode 160. The gate-drain parasitic capacitance in the pixelstructure 100 is determined by the overlapping area of the extendingelectrode 170 and the contact part 162 and the overlapping area of thegate electrode 130 and the drain electrode 160.

In the manufacturing process of the pixel structure 100, themisalignment causes the drain electrode 160 to shift along the directionD or the opposite direction of the direction D relative to the gateelectrode 130. If the drain electrode 160 shifts along the direction D,the overlapping area of the connecting part 166 and the gate electrode130 is increased. At the same time, the contact part 162 is shiftedclose to the gate electrode 130 along the direction D, and theoverlapping area of the contact part 162 and the extending electrode 170is therefore decreased. In this embodiment, the connecting part 166 hasa first width W1, and the first end 172 of the extending electrode 170has a second width W2. The first width W1 is substantially equal to thesecond width W2. Although the misalignment is generated during theprocess in the pixel structure 100, a sum of the overlapping area of theextending electrode 170 and the contact part 162 and the overlappingarea of the gate electrode 130 and the drain electrode 160 is notchanged. This means the gate-drain parasitic capacitance in the pixelstructure 100 can be maintained constantly.

In this embodiment, the first width W1 is substantially equal to thesecond width W2, and the increase of the overlapping area of theconnecting part 166 and the gate electrode 130 is substantially equal tothe decrease of the overlapping area of the contact part 162 and theextending electrode 170 when the misalignment is generated. Similarly,if the misalignment causes the drain electrode 160 to shift toward theopposite direction of the direction D relative to the gate electrode130, the decrease of the overlapping area of the connecting part 166 andthe gate electrode 130 is substantially equal to the increase of theoverlapping area of the contact part 162 and the extending electrode170. According to the pixel structure 100, although the misalignment isgenerated, the gate-drain parasitic capacitance in the pixel structure100 will be equal to the predetermined value. In other words, when thedrain electrode 160 overlaps the gate electrode 130 to form a firstoverlapping area, and the drain electrode 160 overlaps the extendingelectrode 170 to form a second overlapping area, the sum of the firstoverlapping area and the second overlapping area will not vary due tothe misalignment. Therefore, the tolerance of the pixel structure 100for the misalignment is higher than that of the conventional pixelstructure, and a better display picture quality is obtained.

In addition, the electrode part 164 is U-shaped, and the sourceelectrode 150 is L-shaped. A first end of the L-shaped source electrode150 is connected to the data line 120, and a second end of the L-shapedsource electrode 150 is surrounded by the U-shaped electrode part 164.Specifically, the U-shaped electrode part 164 has a base 164 a and twobranches 164 b, 164 c extending from two ends of the base 164 a towardthe scan line 110. A first end of the connecting part 166 is connectedto one of the branches 164 c.

Although the TFT design of the present invention has been describedabove, the present invention is not limited thereof.

FIG. 3 is a schematic diagram illustrating a sectional top view of apixel structure according to a second embodiment of the presentinvention. As shown in FIG. 3, the pixel structure 200 is similar to theabove-mentioned pixel structure 100, and the same numerals in FIG. 1 andFIG. 3 denote the same components. The difference between both is thedesign of the source electrode 250 and the drain electrode 260. Thedrain electrode 260 of the pixel structure 200 also has a U-shapedelectrode part 264. As compared with the above-mentioned embodiment, inthe drain electrode 260, the connecting part 166 is connected to thebase of the U-shaped electrode part 264. In addition, the sourceelectrode 250 of this embodiment has a strip shape. A first end of thesource electrode 250 is connected to the data line 120, and a second endof the source electrode 250 is surrounded by the U-shaped electrode part264.

It is to be noted that the pixel structure 200 also includes theextending electrode 170 and the semiconductor pattern 190. The first end172 of the extending electrode 170 points to the semiconductor layer 140along the direction D, and the overlaps the contact part 162. Thesemiconductor pattern 190 is disposed between the first end 172 of theextending electrode 170 and the contact part 162. Similarly, the effectof the capacitor due to the overlapping of the extending electrode 170and the contact part 162 is substantially equivalent to the effect ofthe capacitor between the electrode part 264 and the gate electrode 130.In addition, the first end 172 of the extending part 170 and theconnecting part 162 have the same width, and the first end 172 of theextending part 170 and the connecting part 166 are respectively disposedat two opposite sides of the contact part 162. The gate-drain parasiticcapacitance in the TFT still does not vary after the drain electrode 260shifts horizontally relative to the gate electrode 130. Therefore, thedisplay picture quality of the pixel structure 200 is excellent, and thepixel structure 200 will not be negatively affected by the misalignment.

FIG. 4 is a sectional top view of a pixel structure according to a thirdembodiment of the present invention. As shown in FIG. 4, the pixelstructure 300 has the same design as the pixel structure 100 except thatthe design of the source electrode 350 and the drain electrode 360 isdifferent from the design of the pixel structure 100, and the samenumerals in FIG. 1 and FIG. 4 denote the same components.

The pixel structure 300 has a U-shaped source electrode 350. Theelectrode part 364 and the connecting part 166 of the drain electrode360 constitute a strip pattern, and the U-shaped source electrode 350surrounds the electrode part 364. Actually, the electrode part 364 andthe connecting part 166 are respectively different parts of the strippattern. The electrode part 364 is the part of the strip patternsurrounded by the source electrode 350, and the connecting part 166 isthe part of the strip pattern extending from the contact part 162 intothe region of the gate electrode 130 along the direction D.

In this embodiment, the pixel structure 300 also has a constantgate-drain parasitic capacitance. That is, the embodiment also includesthe extending electrode 170 connected to the scan line 110 and thecorresponding semiconductor pattern 190. The extending electrode 170overlaps the contact part 162, and the semiconductor pattern 190 isdisposed at the overlapping area of the extending electrode 170 and thecontact part 162. Furthermore, the first width W1 of the connecting part166 is equal to the second width W2 of the first end 172 of theextending electrode 170. When the relative deviation between the gateelectrode 130 and the drain electrode 360 occurs, the overlapping areaof the drain electrode 360 and the extending electrode 170 and theoverlapping area of the drain electrode 360 and the gate electrode 130will vary accordingly. Although the misalignment is generated during themanufacturing process, the pixel structure 300 also has the sameoperating efficiency as the predetermined layout. The gate-drainparasitic capacitance is the same as that of the predetermined layout.Therefore, the pixel structure 300 has a higher tolerance formisalignment, and the display picture quality is easily controlled.

Furthermore, FIG. 5 is a schematic diagram showing a sectional top viewof a pixel structure according to a fourth embodiment of the presentinvention. As shown in FIG. 5, the design of the pixel structure 400 isderived from the pixel structure 300, and the same numerals in the pixelstructure 300 and the pixel structure 400 denote the same components. Inorder to keep the gate-drain parasitic capacitance stable, the drainelectrode 460 of the pixel structure 400 further includes a protrusionpart 468. The contact part 162 is disposed between the connecting part166 and the protrusion part 468. It should be noted that the protrusionpart 468 is parallel to the direction D, and overlaps the extendingelectrode 170 in this embodiment.

In this embodiment, a side of the contact part 162 away from theconnecting part 166 extends outside the contact part 162 to form theprotrusion part 468, and the protrusion part 468 overlaps the extendingelectrode 170 in order to keep the stability of the gate-drain parasiticcapacitance. Moreover, in order to ensure that the gate-drain parasiticcapacitance does not vary due to the misalignment, the protrusion part468 has a third width W3, and the third width W3 is at least equal to orlarger than the second width W2. The first width W1 is also equal to thesecond width W2. That is, the first end 172 of the extending electrode170 in a direction of width is fully covered with the protrusion part468. The pixel structure 400 can have a good display picture quality,and the tolerance for the misalignment also is greatly improved.

The above-mentioned embodiments describe the L-shaped extendingelectrode, but the shape of the extending electrode also can varyaccording to different designs of the pixel structure. FIG. 6 depicts asectional top view of a pixel structure according to a fifth embodimentof the present invention. As shown in FIG. 6, the pixel structure 500includes a scan line 510, a data line 120, a gate electrode 530, asemiconductor layer 140, a source electrode 550, a drain electrode 560,an extending electrode 570, a pixel electrode 180 and a semiconductorpattern 190. The scan line 510 and the data line 120 cross each other,and are electrically insulated from each other. The gate electrode 530is substantially a part of the scan line 510. The semiconductor layer140 is disposed on the gate electrode 530. The source electrode 550 hasat least a portion disposed on the semiconductor layer 140, and thedrain electrode 560 has at least a portion disposed on the semiconductorlayer 140. The source electrode 550 is connected to the data line 120.The extending electrode 570 is connected to the scan line 510, and theextending electrode 570 is substantially extended from the gateelectrode 530. In other words, the extending electrode 570 of thisembodiment is connected to the gate electrode 530. The pixel electrode180 is connected to the drain electrode 560. Furthermore, thesemiconductor pattern 190 is disposed between the extending electrode570 and the drain electrode 560, and is disposed at the overlapping areaof the extending electrode 570 and the drain electrode 560.

The extending electrode 570 of this embodiment is U-shaped. A first end572 of the extending electrode 570 is not connected to any othercomponent, and a second end of the extending electrode 570 is connectedto the gate electrode 530. The drain electrode 560 includes a contactpart 562, an electrode part 564, a connecting part 566 and a protrusionpart 568.

The contact part 562 is disposed outside the scan line 510 and the gateelectrode 530. The electrode part 564 is disposed on the semiconductorlayer 140, and the electrode part 564 is surrounded by the U-shapedsource electrode 550. The connecting part 566 is partially disposedoutside the gate electrode 530, and extends from the contact part 562 toconnect the electrode part 564 along the direction D. The protrusionpart 568 is parallel to an edge of the gate electrode 530, and does notoverlap the gate electrode 530. The protrusion part 568 is connected tothe contact part 562, and overlaps the extending electrode 570.

In this embodiment, the extending electrode 570 has the first end 572that is not connected to any component. The first end 572 points to thesemiconductor layer 140 along the direction D, and overlaps theprotrusion part 568 of the drain electrode 560. When a misalignment isgenerated along the direction D or the opposite direction of thedirection D during the alignment step, the relative position between thegate electrode 530 and the contact part 562 will be closer or farther.When the relative position between the gate electrode 530 and thecontact part 562 is closer, the overlapping area of the connectingelectrode 566 and the gate electrode 530 is increased, and theoverlapping area of the protrusion part 568 and the extending electrode570 is reduced. On the contrary, when the relative position between thegate electrode 530 and the contact part 562 is farther, the overlappingarea of the connecting part 566 and the gate electrode 530 is reduced,and the overlapping area of the protrusion part 568 and the extendingelectrode 570 is increased.

The extending electrode 570 and the gate electrode 530 are electricallyconnected to each other. Similarly, the effect of the capacitor due tothe overlapping of the extending electrode 570 and the protrusion part568 is substantially equivalent to the effect of the capacitor due tothe overlapping of the connecting part 566 and the gate electrode 530.Based on this relation, the gate-drain parasitic capacitance in thepixel structure 500 is determined by the overlapping area of theextending electrode 570 and the protrusion part 568 and the overlappingarea of the connecting part 566 and the gate electrode 530. In order tomaintain the overlapping area of the gate electrode 530 and the drainelectrode 560, a first width W1 of the connecting part 566 issubstantially equal to a second width W2 of the first end 572. The drainelectrode 160 overlaps the gate electrode 130 to form a firstoverlapping area, and the drain electrode 160 overlaps the extendingelectrode 170 to form a second overlapping area. When the relativedeviation between the gate electrode 530 and the drain electrode 560occurs due to the misalignment during the manufacturing process of thepixel structure 500, the sum of the first overlapping area and thesecond overlapping area will not vary. Therefore, the gate-drainparasitical capacitance in the pixel structure 500 is maintained, andwill not vary due to the misalignment. The pixel structure 500 has agood display picture quality and stable device characteristic.

In summary, the present invention disposes an extending electrodeelectrically connected to the gate electrode in the pixel structure, andan end of the extending electrode overlaps the drain electrode. When themisalignment is generated during the manufacturing process of the pixelstructure, the gate-drain parasitic capacitances still are the same asthat of the predetermined layout. For this reason, the pixel structurehas a good display picture quality, and a problem of image flicker isnot easily generated in the application of display. The tolerance forthe misalignment of the pixel structure in the present invention alsocan be greatly improved.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention.

What is claimed is:
 1. A pixel structure, comprising: a scan line and adata line, crossing each other and electrically insulated from eachother; a gate electrode, electrically connected to the scan line; asemiconductor layer, disposed on the gate electrode; a source electrode,having at least a portion disposed on the semiconductor layer, andconnected to the data line; a drain electrode, having at least a portiondisposed on the semiconductor layer, the drain electrode comprising: acontact part, disposed outside the gate electrode; an electrode part,disposed on the semiconductor layer; and a connecting part, extendingfrom the contact part along a direction to connect the electrode partand overlapping a portion of the gate electrode, and the connecting parthaving a first width; an extending electrode, connected to the scanline, the extending electrode having a first end pointing to thesemiconductor layer along the direction and overlapping the drainelectrode, the extending electrode having a second width, and the firstwidth being substantially equal to the second width; and a pixelelectrode, connected to the contact part of the drain electrode.
 2. Thepixel structure of claim 1, further comprising a semiconductor pattern,disposed between the extending electrode and the drain electrode andlocated at an overlapping area of the extending electrode and the drainelectrode.
 3. The pixel structure of claim 1, wherein the extendingelectrode has a second end away from the first end, and the second endis connected to the scan line.
 4. The pixel structure of claim 3,wherein the extending electrode is L-shaped.
 5. The pixel structure ofclaim 3, wherein the extending electrode is substantially U-shaped. 6.The pixel structure of claim 1, wherein the electrode part of the drainelectrode is a U-shaped part surrounding the source electrode, and theU-shaped part has a base and two branches extending from two ends of thebase toward the direction.
 7. The pixel structure of claim 6, whereinthe connecting part of the drain electrode is connected to the base orone of the branches of the U-shaped part.
 8. The pixel structure ofclaim 1, wherein the source electrode has a U-shape so that it surroundsthe electrode part of the drain electrode.
 9. The pixel structure ofclaim 8, wherein the electrode part of the drain electrode and theconnecting part are connected to each other, and form a strip pattern.10. The pixel structure of claim 1, wherein the drain electrode furthercomprises a protrusion part, the contact part is disposed between theconnecting part and the protrusion part, and the protrusion part isparallel to the direction and overlaps the extending electrode.
 11. Thepixel structure of claim 1, wherein the drain electrode furthercomprises a protrusion part, parallel to an edge of the gate electrodeand located outside the gate electrode, and the protrusion part isconnected to the contact part and overlaps the extending electrode. 12.The pixel structure of claim 1, wherein the contact part, the electrodepart and the connecting part of the drain electrode are formedintegrally.
 13. The pixel structure of claim 1, wherein the sourceelectrode and the data line are formed integrally.
 14. The pixelstructure of claim 1, wherein the gate electrode is a portion of thescan line.
 15. The pixel structure of claim 14, wherein the extendingelectrode is connected to the gate electrode.
 16. The pixel structure ofclaim 1, wherein the gate electrode extends from the scan line to format least a portion of the gate electrode outside the scan line.